Article info

Keywords

• difficulty parameters
• The Ability Estimation
• positive and negative skewed
• Information Function
• normal distribution

Abstract

This study investigated the Effect of Test Length and Ability distribution form on The Estimation of a person's Ability, item difficulty, and the information function of test and its items, According to Rasch Model in Item Response Theory (IRT). Among the procedures of the study was to generate data and items were also generating the examinee's ability, the generated data rate (1000) were examined, for all variables; test length (30, 60) item, and Ability distribution (normal, positive and negative skewed) according to Item Response Theory Models (one-parameter). According to the analysis of data depending on the softwares (BILOG-MG), (WINGEN) and (SPSS), The results showed that there were statistically significant differences at (α=0.05) among the standard error means of item in the estimation of difficulty parameters, such estimations in a person's ability were more accurate in the positive and negative skewed. The test consisted from 30 items. Also The results showed there were statistically significant differences (α=0.05) among the standard error means of item in the estimation of difficulty parameters for the test consisted from 30 items, which provided the most information. The researcher recommends further research depending on other parametric models, also by using real data.